Bill Prady and Chuck Lorre got the chance to shoot two different pilots for The Big Bang Theory. The second pilot aired and was a success, while the first was not a hit. A major reason for it was the introduction of a main character named Katie. According to Bill Prady, her involvement proved to be a liability for the show.
Prady tells EW, "Well, that pilot was actually the second pilot we had done after the first one didn't work for a bunch of reasons. In the first pilot, the female character (who, at that point, was named Katie) is kind of rough. She's dangerous in a way and wasn't very nice to the guys. I remember going to the test screening, the dial testing..."
Chuck Lorre also realized that Katie's character was flawed given that the audience saw Leonard and Sheldon as vulnerable.
"We didn't realize early on that the audience viewed them as children. They were very naive and childlike, regardless of how intelligent they were. They were very vulnerable, and the audience didn't want a toxic presence around them.
He continues, "That's why we rewrote Katie to become Penny [Kaley Cuoco] and made her much more charmed by the guys and kind to them, as opposed to a woman who would take advantage of them."
There was another problem with the cast that took place behind the scenes. However, this time, Lorre was strict about not letting this particular cast member go, despite CBS' request.
Making his way to New York, Chuck Lorre was set to meet the higher-ups alongside the cast. However, once Lorre took part in the meeting, he realized Kunal Nayyar was absent. At this point, Lorre was briefed that Nayyar would not be attending and was told that his part would be recast. Lorre was not pleased with this decision and fought for the young actor, who was not an established name at the time.
Lorre reveals, "When I landed in New York for the upfronts, I was informed that Kunal wasn't there. I was like, "What do you mean he isn't here? Why isn't he here?" Apparently while I was flying across the country, a CBS executive determined—unilaterally—that Kunal wasn't right for the role and we would recast that part. Well, I did not respond well. I was furious. They made this decision without consulting me."
Lorre fought to reverse the decision given that Nayyar wasn't given much of a chance either, given he had limited dialogue during the pilot.
"If you go back and watch the pilot, we didn't really give him much of a chance in that episode. It wasn't because Kunal didn't deliver, it was because we still hadn't quite landed on his character."
As fans know by now, Nayyar stayed onboard and there was no intent on replacing his character at any point.
No, there wasn't any type of gameplan to replace Kunal Nayyar at any point. Lorre made it clear that the actor wasn't going anywhere, and that he was taking responsibility for his early shortcomings.
He revealed, "I called the execs at CBS and said, "You can't fire him. I cast him, I believe in him, I'll take responsibility for this decision. He's my guy." If I'm going to fail, I'm going to fail on my own choices. I'm not going to fail on someone else's choices. I wasn't about to recast that part because someone else made a decision. It seemed so unfair to cut the actor from the series based on what—the two lines where he whispered to Wolowitz?"
Keeping Nayyar onboard proved to be the correct decision as Raj turned into a major fan favorite, and another part of the sitcom's remarkable longevity through the years.